Organic waste treatment system

ABSTRACT

[Object] To provide an organic waste treatment system in which general wastes from home, ordinary offices, and the like as well as industrial wastes including sludge, waste plastics, and the like can be subjected to treatment such as decomposition by a hydrothermal reaction under a subcritical water condition and in which treated wastes can be taken out in a dried state, sorted, and recycled. 
     [Approach] In a waste treatment system for hydrolyzing organic wastes while stirring the wastes under a high-temperature and high-pressure environment and thermally decomposing or carbonizing the wastes in a double-walled pressure-resistant container  1 , the system includes at least: water vapor supply means  9   a  for supplying high-heat saturated water vapor into the container  1 ; pressure regulating means  10  for regulating pressure in the container  1  by using an on-off valve; and stirring means  6  having a shaft  7  for stirring the charged wastes in the container  1  and provided to penetrate the container  1  and the system includes the steps of: hydrolyzing the wastes while adjusting temperature to 230° C. or higher and pressure to 3 MPa in the container  1  and stirring the wastes and thermally decomposing or carbonizing the wastes; adjusting the pressure in the container  1  to atmospheric pressure or lower and discharging the treated wastes out of the container while maintaining a dried state of the wastes; and sorting the discharged treated wastes and forming at least one of fertilizer, feed, and auxiliary fuel depending on types of the wastes.

TECHNICAL FIELD

The prevent invention relates to an organic waste treatment system inwhich general wastes from home, ordinary offices, and the like as wellas industrial wastes including sludge, waste plastics, and the like canbe subjected to treatment such as decomposition by a hydrothermalreaction under a subcritical water condition and in which treated wastescan be taken out in a dried state, sorted, and recycled.

BACKGROUND TECHNIQUE

In a prior-art organic waste treatment system, wastes to be treated areseparated in advance and the separated wastes are respectively chargedinto treatment apparatuses designed according to types of the wastes.For example, the waste plastics are charged into and treated in aplastic-specific treatment apparatus, rubber such as waste tires ischarged into and treated in a rubber-specific treatment apparatus, wastenewspaper, wastepaper, and the like are charged into and treated in atreatment apparatus for paper, and garbage is charged into and treatedin a garbage-specific treatment apparatus, respectively.

Moreover, how to treat varies among types of the wastes. The wastepaperis subjected to incineration in an incinerator. The waste newspaper isdissolved in a special solvent and recycled. The waste plastics andwaste rubber are dissolved again and formed into structural materials orthermally decomposed and used as solid fuel or liquid fuel. The garbageis dried and used as fertilizer or animal feed.

For example, there are disclosed an apparatus for solidifying plasticwastes in Patent Document 1, an apparatus for treating the waste plasticto turn it into fuel in Patent Document 2, a treatment system for makingfeed and fertilizer in Patent Document 3, and a method and an apparatusfor treating medical wastes by heating in Patent Document 4.

However, because the treatment apparatuses are designed according to thetypes of the wastes and how to treat them as described above, thetreatment apparatus for the waste plastics cannot be used for treatmentof rubber or garbage and the treatment apparatus for making feed andfertilizer cannot be used for treatment of the waste plastics, forexample. Therefore, the treatment apparatuses adapted to the respectivetypes of the wastes and how to treat them are necessary. However, it isclose to impossible for local small municipalities to have so manytreatment apparatuses.

Moreover, not all of wastes can be easily separated into the wasteplastics, rubber, wastepaper, garbage, and the like. If anything, amajor part of them cannot be separated. Especially because compositematerials are used everywhere in recent products and many of theproducts cannot be separated easily even by disassembly. For example,there are an infinite number of inseparable wastes such as pieces ofmetal or glass protected by plastic, electric, wires, metal plates orplastic plates on which rubber sheets are laminated, a plate into whicha nail is driven, plastic products in which metal springs, pins, andgears are embedded, books including many sheets of synthetic paper. Ifthey are treated by the above treatment apparatuses, the apparatusesbreak.

The above composite materials are normally collected as unburnablewastes. However, many of wastes collected as burnable wastes are notrecommended for incineration in an incinerator. For example, animalcarcasses, animal feces and urea, food residue, rotten sea food and farmproduce give out foul smells to surroundings when they are incinerated.There are also infectious wastes from hospitals and the like, and morespecifically, used bandages, cotton, diapers, sheets, and the like frommedical institutions and medical sites such as hospitals. These wastesare collected by specialized sanitation engineers and need be sterilizedor disinfected before incineration, because pathogens, bacteria,viruses, and the like may be released into the atmosphere or may remainin incineration ash if the collected wastes are incinerated as they arein the incinerator.

There is also litter laid on floors of containers and vehicles intransporting and conveying horses, cattle, pigs, and the like. Becausethe horses and the like directly excrete feces and the like onto thelitter, it is necessary to dispose of feces and urine together with thelitter. However, microbes and bacteria propagate in such litter and theymay not die but be released into the atmosphere together with smokeexhaust or remain in incineration ash if the litter is incinerated in anincinerator.

In recent years, incineration of wastes in incinerators is subjected tocriticism from a viewpoint of global environment protection and theincineration of waste plastics in the incinerators may damage theincinerators or generate harmful substances such as dioxin and istherefore strictly restricted by laws, ordinances, and the like.

Therefore, development of a method and an apparatus for disposing ofcomposite materials which cannot be separated easily and for suitablydisposing of wastes which are not recommended for incineration in theincinerator is an urgent necessity. Inventors of the present inventionhave developed a method and an apparatus for this purpose before and hasalready filed a patent application (Patent Document 5). In PatentDocuments 6, 7, and 8, similar methods and apparatuses are proposed.

A system disclosed in Patent Document 5 is for treating wastes and othergeneral materials under a high-temperature and high-pressure environmentso that they can be recycled into heat generating molded body and is anexcellent system. However, gas and vapor in a pressure-resistantcontainer are released outside when the container is opened after thetreatment and pathogens, microbes, bacteria, and the like may bedispersed into the atmosphere if they still exist. In this point, thesystem has still some room for improvement.

Decomposition treatment method and apparatus disposed in Patent Document6 are for performing decomposition treatment of persistent wastes at atemperature of critical or lower pressure by utilizing a hydrothermalreaction. Because they are of a continuous type, the apparatus becomescomplicated.

A method of treating organic wastes disclosed in Patent Document 7 is amethod of performing oxidation in high-temperature and high-pressurevapor equal set of temperature equal to or higher than the supercriticaltemperature and pressure lower than the supercritical pressure of water.Because the set temperature is as high as 500° C. or higher and the setpressure is as high as 5 MPa to 22 MPa, it is difficult and expensive todevelop the apparatus resistant to such temperature and pressure.

A high-temperature and high-pressure treatment apparatus disclosed inPatent Document 8 is for continuously oxidizing organic wastes in astate of supercritical or subcritical water. Because treatmentconditions of subcritical water suitable for an oxidative decompositionreaction are temperature of 250° C. or higher and treatment pressure of5 to 10 MPa, it is difficult and too expensive to develop the apparatusfor continuously performing oxidation under these conditions.

In the above inventions disclosed in Patent Documents 5 to 8, the wastesare decomposed by using the hydrothermal reaction. For taking thedecomposed wastes out of the treatment apparatus, temperature andpressure in the apparatus are returned to room temperature andatmospheric pressure. As a result, water vapor returns to a state ofwater to make the treated wastes swamped and make it difficult to takethe wastes out of the apparatus. Recycling of the treated wastesrequires drying of the wastes again and is too expensive.

Patent Document 1: Japanese Patent Application Laid-open No. 2005-178327Patent Document 2: Japanese Patent Application Laid-open No. 6-91649Patent Document 3: Japanese Patent Application Laid-open No. 2004-262720Patent Document 4: Japanese Patent Application Laid-open No. 2002-102819Patent Document 5: Japanese Patent Application Laid-open No. 2004-321855Patent Document 6: Japanese Patent Application Laid-open No. 10-147662Patent Document 7: Japanese Patent No. 3440835 Patent Document 8:Japanese Patent Application Laid-open No. 2004-290819 DISCLOSURE OF THEINVENTION Problems to be Solved by the Invention

With the above problems of the prior-art waste treatment apparatuses inview, it is an object of the present invention to provide an organicwaste treatment system in which general wastes from home, ordinaryoffices, and the like in addition to industrial wastes including sludge,waste plastics, and the like can be subjected to treatment such asdecomposition by a hydrothermal reaction under a subcritical watercondition and in which treated wastes can be taken out in a dried state,sorted, and recycled.

Means to Solve the Problems

To achieve the above object, according to the invention, there isprovided an organic waste treatment system for hydrolyzing organicwastes while stirring the wastes under a high-temperature andhigh-pressure environment and thermally decomposing or carbonizing thewastes in a double-walled pressure-resistant container, wherein thesystem comprises at least: water vapor supply means for supplyinghigh-heat saturated water vapor into the container; pressure regulatingmeans for regulating pressure in the container by using an on-off valve;and stirring means having a shaft for stirring the charged wastes in thecontainer and provided to penetrate the container and the systemincludes the steps of: hydrolyzing the wastes while adjustingtemperature to 230° C. or higher and pressure to 3 MPa in the containerand stirring the wastes and thermally decomposing or carbonizing thewastes; adjusting the pressure in the container to atmospheric pressureor lower and discharging the treated wastes out of the container whilemaintaining a dried state of the wastes; and sorting the dischargedtreated wastes and forming at least one of fertilizer, feed, andauxiliary fuel depending on types of the wastes.

According to the invention, in the above structure, the system mayfurther comprise forcibly discharging means for forcibly dischargingwater vapor to discharge the water vapor generated in drying to anoutside of the pressure-resistant container and the discharged watervapor may be used to operate a gas turbine to generate electricity byusing the power. Moreover, the dried state of the treated wastes ispreferably maintained by supplying high-heat water vapor into aclearance between an outer wall and an inner wall of the double wall ofthe pressure-resistant container and maintaining temperature at 160 to180° C. and pressure at 1 MPa in the clearance.

The organic wastes to be treated by the system of the invention are atleast one type of industrial wastes of sludge, waste plastics,wastepaper, wood waste, animal solid wastes, plant and animal residue,animal feces and urine, animal carcasses, and infectiousspecially-controlled industrial wastes and are at least one type ofgeneral wastes of general wastes from business activities, householdwastes, infectious specially-controlled general wastes, separatedgarbage, and food residue.

In the system of the invention, auxiliary fuel is formed as powder orpellets. Incineration ash after use of the auxiliary fuel can be moldedby a molding device and used as structural materials.

Next, specific examples of the organic wastes which can be treated bythe system of the invention are used litter, garbage such as rotten meatand vegetables, sea food residue, and unsold box lunches, wrappingpaper, corrugated cardboard, plastics such as plastic packages and bags,plastic bottles, and Styrofoam, timber chips, felled trees, grass,sludge accumulated in sewers and rivers, treated sludge from watertreatment plant, and stockbreeding wastes.

Here, a principle of treatment of the invention will be described. Thesystem of the invention is a high-temperature and high-pressuresterilization apparatus. Because objects to be treated are limited toorganic wastes and the organic wastes are made sterile and harmless,treatment under supercritical water condition is unnecessary and thehydrothermal reaction under the subcritical water condition issufficient. For the treatment, saturated water vapor is supplied intothe apparatus to thereby carry out the treatment under the subcriticalcondition. In other words, the treatment is carried out inhigh-temperature and high-pressure water.

In general, water is characterized by a high dissociation property and ahigh dielectric constant. In water at room temperature, acid or alkalineproperty develops depending on hydrogen ion concentration. A reaction inwhich hydrogen ion and hydroxide ion of water react respectively todecompose a substance is known as hydrolysis. A union through oxygen ofan inorganic compound or an organic compound, i.e., ester and etherlinkages in case of an organic compound and oxides in case of aninorganic compound, is decomposed by water by mutually using hydroxidesas bridges.

Moreover, in the high-temperature and high-pressure state, a degree ofdissociation of water increases as the temperature rises, reaches itspeak around 250° C., and then decreases. This means that acid oralkaline property of water is considerably affected by variation oftemperature. In other words, under subcritical saturated vapor pressure,because the degree of dissociation of water is high, acid and alkalineproperties are strong and water becomes a reactive solvent. Therefore,in subcritical water, hydrolysis reaction is caused by reactive watermolecules and the reaction becomes the most intense around 300° C.

Moreover, because a gaseous phase and a liquid phase are mixed under thesaturated vapor pressure, a hydrolysis reaction takes precedence in theliquid phase and a dehydration condensation reaction takes precedence inthe gaseous phase. In general, under the subcritical saturated vaporpressure, it is said that an ionic reaction and the hydrolysis reactionaccelerate in the liquid phase and that a radical reaction takesprecedence in the gaseous phase. Such reactions in the subcritical waterand supercritical water are known as hydrothermal reactions.

As described above, the system of the invention utilizes thehydrothermal reaction under the subcritical saturated vapor pressure anddoes not discharge inner air before treatment. Therefore, the treatmentis carried out in the presence of oxygen and an oxidation reactionoccurs due to the presence of oxygen in a low-temperature region ofabout 230° C. The oxidation reaction is a reaction for taking electrons.In general, it becomes easier to take and give electrons through themedium of water. The oxidation reaction under such a hydrothermalcondition is known as a hydrothermal oxidation reaction.

The system of the invention can treat waste plastics as well as easilydecomposable litter, medical wastes, and the like out of organic wastes.Major waste plastics, i.e., polyolefin, polystyrene, and polyvinylchloride are thermally decomposed depending on temperature in general.However, it is known that these plastics of thermostability of polyvinylchloride, polystyrene, and polyolefin is high in that order and that arate of volatility in a vacuum is extremely low at about 200° C. and acontribution of thermal decomposition to the treatment in the system ofthe invention is considered to be small. In the system of the invention,it is assumed from the above-described reaction mechanism in thesubcritical water that the waste plastics are decomposed by thehydrolysis reaction and ionic reaction in the liquid phase and by thedehydration condensation reaction, radical reaction, thermaldecomposition, and hydrothermal oxidation in the gaseous phase under thesubcritical water condition of 230° C. Moreover, the treatment residueis assumed to be undecomposed waste plastics. Such decomposed mattersare discharged from the system of the invention together with the vapor,pass through the cyclone where dust or the like is removed, and most ofthe remaining vapor is cooled and liquefied by gas-liquid contact withcooling water in the capacitor and subjected to microbial treatment andwastewater treatment by using activated carbon. The undecomposed mattersin the surplus gas are subjected to secondary treatment by a burningmethod and discharged.

EFFECTS OF THE INVENTION

According to the present invention, by using one organic waste treatmentsystem, it is possible to carry out treatment such as decomposition bythe hydrothermal reaction under the subcritical water condition ofindustrial wastes such as sludge, waste plastics, wastepaper, woodwaste, animal solid waste, plant and animal residue, animal feces andurine, animal carcasses, and infectious specially-controlled industrialwastes and general wastes such as general wastes from businessactivities, household wastes, infectious specially-controlled generalwastes, separated garbage, and food residue and it is also possible totreat composite materials which cannot be separated. Therefore, it isunnecessary to provide a plurality of treatment apparatuses forrespective types of the wastes as in the prior-art systems to therebyreduce the treatment cost.

Moreover, because the system of the invention can sterilize and kill themicrobes and bacteria propagating in the litter and pathogens adheringto the medical wastes by the hydrothermal oxidation reaction under thehigh-temperature and high-pressure condition by using water vapor, it ispossible to obtain a particular effect of easily treating the wasteswhich could not be treated before disinfection or sterilization in theprior art.

Furthermore, because the system of the invention carries out treatmentsuch as decomposition of the organic wastes in a hermetically sealedcontainer, it is possible to obtain an effect of not exhaling foulsmells outside even during treatment of garbage, stockbreeding wastes,sludge, rotten sea food, meat, and farm produce.

Moreover, because the wastes to be treated are different depending onseason and the time of day or year, the system of the invention cantreat the waste plastics and waste rubber together when there are largeamounts of them. It is also possible to take the treated wastes out ofthe pressure-resistant container in the dried state and to recycle themas auxiliary fuel. Moreover, when there are large amounts of litter,animal solid wastes, plant and animal residue, animal feces and urine,animal carcasses, sea food, and the like, it is possible to obtain aneffect of treating them together, taking the treated wastes out of thepressure-resistant container in the dried state, and recycling them asfeed and fertilizer.

BEST MODES FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described based onthe drawings. FIG. 1 is a sectional view of an example of an organicwaste treatment apparatus A of a waste treatment system of the presentinvention. FIG. 2 is a block diagram of an example of the wastetreatment system of the invention into which the treatment apparatus Aof FIG. 1 is integrated.

In FIG. 1, a reference numeral A designates an organic waste treatmentapparatus which is a main portion of a waste treatment system of theinvention, 1 designates a double-walled heat-resistant andpressure-resistant container forming the organic waste treatmentapparatus A, 1 a designates an outer wall of the heat-resistant andpressure-resistant container 1, and 1 b is an inner wall of the same. Aproper clearance k is provided between the outer wall 1 a and the innerwall 1 b. In the clearance k high-temperature vapor is supplied andcirculates as will be described later. As the heat-resistant andpressure-resistant container 1, a container resistant to internaltemperature of 600° C. and internal pressure of 5 MPa is used here.

A reference numeral 2 designates a waste charge port through whichwastes are charged into the heat-resistant and pressure-resistantcontainer 1 and 3 designates a waste charging device for storing thewastes to be charged into the heat-resistant and pressure-resistantcontainer 1 through the waste charge port 2 and charging the wastes atproper intervals while maintaining hermeticity. A reference numeral 4designates a discharge port of treated wastes that have been subjectedto treatment such as decomposition in the heat-resistant andpressure-resistant container 1 and 5 designates a discharge pipe mountedto the discharge port 4.

A reference numeral 6 designates a screw blade as a stirring meansprovided in the heat-resistant and pressure-resistant container 1. Thescrew blade 6 is attached to a shaft 7 provided to penetrate thecontainer 1 and rotated by a motor 8. The wastes charged into theheat-resistant and pressure-resistant container 1 are stirred by thescrew blade 6 and are moved forward and backward in the container 1 bycontrolling the motor 8 for normal and reverse rotations.

A reference numeral 9 designates a vapor generating device, 9 adesignates an intra-container vapor supply device for supplying watervapor generated in the vapor generating device 9 into the heat-resistantand pressure-resistant container 1 and 9 b designates an intra-wallvapor supply device for supplying water vapor generated in the vaporgenerating device 9 into the clearance k between the outer wall 1 a andthe inner wall 1 b of the heat-resistant and pressure-resistantcontainer 1.

A reference numeral 10 designates a pressure regulating device that isconnected to the heat-resistant and pressure-resistant container 1 by aconnecting pipe 10 a and is for adjusting pressure in the container 1 topredetermined pressure by using an on-off valve (not shown). A referencenumeral 11 a designates a pressure sensor for measuring pressure in theheat-resistant and pressure-resistant container 1 and 11 b designates apressure sensor for measuring pressure in the clearance k between theouter wall 1 a and the inner wall 1 b of the heat-resistant andpressure-resistant container 1. A reference numeral 12 a designates atemperature sensor for measuring temperature in the heat-resistant andpressure-resistant container 1 and 12 b designates a temperature sensorfor measuring temperature in the clearance k between the outer wall 1 aand the inner wall 1 b of the heat-resistant and pressure-resistantcontainer 1. By these pressure sensors 11 a, 11 b and the temperaturesensors 12 a and 12 b, the pressure and temperature in theheat-resistant and pressure-resistant container 1 are always monitoredduring treatment of the wastes.

A reference numeral 13 designates a cyclone that is connected to theheat-resistant and pressure-resistant container 1 through the on-offvalve to forcibly draw in the water vapor generated in the container 1and discharge the water vapor out of the container 1. At the same time,surplus gas generated in decomposition of the organic waste is takenout, dust or the like is separated from the gas, and most of theresidual gas and water vapor is cooled and liquefied by gas-liquidcontact with cooling water in a capacitor 14 and subjected to microbialtreatment and wastewater treatment by using activated carbon. Areference numeral 15 designates a wastewater treatment setup 15 for thispurpose, 15 a designates a flow rate regulating tank, 15 b designates anaeration tank, and 15 c designates a discharge tank. A reference numeral16 designates a vacuum pump connected to the capacitor 14, 17 designatesa deodorizing device, and 18 designates a cooling tower and these arefor exhausting surplus gas. The cooling tower 18 has also a function ofdeodorizing a room such as a factory as a scrubber. These also perform afunction of forcibly discharging water vapor in the heat-resistant andpressure-resistant container 1. A reference numeral P1 designates acooling pump, P2 designates a drain pump, h designates exhaust, and fdesignates discharge.

In the invention, the water vapor discharged from the cyclone 13 ishigh-temperature and high-pressure. In order to effectively use thewater vapor, a gas turbine GT is provided upstream from the capacitor 14and is operated to thereby rotate a generator GE to generateelectricity.

A reference numeral 19 is a central control unit of the organic wastetreatment apparatus A. The central control unit 19 controls, based onmeasurement results of pressures and temperatures in the heat-resistantand pressure-resistant container 1 and the clearance k between the outerwall 1 a and the inner wall 1 b by the pressure sensors 11 a, 11 b andthe temperature sensors 12 a, 12 b and through control signal cables,actuation of the all devices provided to the heat-resistant andpressure-resistant container 1, i.e., the waste charging device 3provided to the waste charge port 2, the motor 8 for rotating the screwblade 6, the vapor generating device 9, the intra-container vapor supplydevice 9 a for supplying high-heat saturated water vapor into theheat-resistant and pressure-resistant container 1, the intra-wall vaporsupply device 9 b for supplying water vapor into the clearance k betweenthe outer wall 1 a and the inner wall 1 b of the heat-resistant andpressure-resistant container 1, and on-off valves of the pressureregulating device 10 for regulating pressure in the heat-resistant andpressure-resistant container 1 and the cyclone 13.

In the organic waste treatment apparatus A of the system of theinvention, while the central control unit 19 controls actuation of theabove respective devices, the temperature is regulated to 230° C. orhigher and the pressure is regulated to 3 MPa in the heat-resistant andpressure-resistant container 1 and the screw blade 6 is rotated to stirthe organic wastes in the container 1 to thereby dry, hydrolyze andthermally decompose or carbonize the organic wastes. During drying, theon-off valve of the cyclone 13 is opened to release the generated watervapor out of the heat-resistant and pressure-resistant container 1 butthe pressure regulating device 10 maintains the pressure in theheat-resistant and pressure-resistant container 1 at 3 MPa or higher. Inthe organic waste treatment apparatus A of the system of the invention,the hydrothermal reaction under the subcritical water condition isutilized to decompose the wastes as described above and therefore thetemperature in the heat-resistant and pressure-resistant container 1 ismaintained below 500° C. Because the pressure in the heat-resistant andpressure-resistant container 1 is also increased due to gas generatedduring treatment of the organic waste, the on-off valve is opened totake the surplus gas out of the container 1 to thereby adjust pressurein the container. To take out the gas, the gas is passed through thecyclone 13 to separate dust or the like.

To discharge residues from the discharge port 4 after the treatment ofthe organic wastes, the pressure regulating device 10 adjusts thepressure in the heat-resistant and pressure-resistant container 1 to theatmospheric pressure or lower. Otherwise, the water vapor and gas in theheat-resistant and pressure-resistant container 1 is released at a dashinto the atmosphere and microbes and pathogens may be released togetherinto the atmosphere if they have not died and are remaining in theresidues after the treatment.

Moreover, in the invention, to make it possible to take the treatedwastes out of the heat-resistant and pressure-resistant container 1 inthe dried state, the intra-wall vapor supply device 9 b supplieshigh-temperature water vapor into the clearance k between the outer wall1 a and the inner wall 1 b of the heat-resistant and pressure-resistantcontainer 1 to maintain the temperature at 160 to 180° C. and thepressure at 1 MPa in the clearance k. This is because the water vapor inthe container 1 turns into water, mixes with the treated wastes, andbecomes muddy, if the pressure in the heat-resistant andpressure-resistant container 1 is adjusted to the atmospheric pressureor lower and the temperature in the container 1 is returned to roomtemperature after the treatment of the organic wastes. Incidentally, thetreated wastes that have become muddy cost much labor to take out of theheat-resistant and pressure-resistant container 1 and the wastes need bedried again for recycling, which involves excessively high cost.

5 cubic meters and about 3 tons of litter in which microbes arepropagating was actually charged into the heat-resistant andpressure-resistant container 1 of the organic waste treatment apparatusA of the system of the present invention and treated at pressure of 3MPa and temperature of 230° C. in the container 1 and while normally andreversely rotating the screw blade 6 at a speed of about 36 rotationsper minute. As a result, all of the litter could be carbonized in about30 minutes. The residues in the discharge pipe 5 after the wastes hadbeen taken out of the discharge port 4 were checked and no microbe orbacteria was found.

Similarly, organic medical wastes such as bandages, cotton, and sheetsand including inorganic matters such as syringes given by a sanitationengineer on a trial basis were charged into the heat-resistant andpressure-resistant container 1 and treated at pressure of 3 MPa andtemperature of about 240° C. in the container 1 and while normally andreversely rotating the screw blade 6 at a speed of about 36 rotationsper minute. As a result, all excluding the syringes could be carbonizedin about 40 minutes. Treated wastes taken out of the discharge port 4were checked and no pathogen was found and no pathogen was found in theremaining syringes.

Moreover, garbage such as food residue of meat, vegetables, fish, andthe like and unsold box lunches, paper such as wrapping paper andwastepaper, corrugated cardboard, plastics such as plastic packages andbags, plastic bottles, and Styrofoam were respectively charged into theheat-resistant and pressure-resistant container 1 of the organic wastetreatment apparatus A and submitted to a test and substantially all ofthem could be decomposed. From the plastics, combustible gas or liquidsuch as methane, ethylene, and propylene could be collected as fuel gasor fuel oil.

The above organic waste treatment apparatus A can also treat timberchips, felled trees, grass, sludge, stockbreeding wastes. These wasteswere treated at pressure of 3 MPa and temperature of about 240° C. inthe container 1 and while normally and reversely rotating the screwblade 6 at a speed of about 36 rotations per minute. As a result, mostof them could be treated, e.g., decomposed without generating foulsmells. The wastes which could not be decomposed included no harmfulsubstance such as dioxin and therefore it was found to be safe todispose of them in soil as they are.

Next, with reference to FIG. 2, the organic waste treatment system ofthe invention in which the above organic waste treatment apparatus A isincorporated will be described. The discharge pipe 5 attached to thedischarge port 4 of the organic waste treatment apparatus A is mountedwith a sorting recycling device B for the treated wastes. In the sortingrecycling device B, a reference numeral 20 designates a dischargeconveyer connected to the discharge pipe 5 and 21 designates a hopperfor temporarily storing the treated wastes sent by the conveyer 20.

A reference numeral 22 designates a sorter for sorting the treatedwastes stored in the hopper 21 according to properties of them. If thesorter 22 determines that the treated wastes are suitable forfertilizer, the sorter 22 sends the wastes to a fertilizer formingsystem 23 and stores them as fertilizer in a fertilizer storage portion24. The treated wastes suitable for fertilizer are wastes treated in theorganic waste treatment apparatus A including sludge, animal solidwaste, plant and animal residue, animal feces and urine, animalcarcasses, general wastes from business activities, household wastes,separated garbage, food residue, and the like as well as used litter,rotten meat and vegetables, sea food residue, and the like.

If the sorter 22 determines that the treated wastes are suitable forfeed, the sorter 22 sends the wastes to a feed storage portion 25 andstores them as feed. Wastes suitable for feed include animal solidwastes, animal carcasses, plant and animal residue, separated garbage,and the like.

Moreover, if the sorter 22 determines that the treated wastes aresuitable for auxiliary fuel, the wastes are treated by a steam dryer 26and then sifted through a sieve 27 to remove waste metal such as ironand copper, cans, glass, rubber not suitable for burning, pottery, andother foreign matter which are unnecessary solids and send them to anunnecessary matter collecting portion 28. Unnecessary solids are alsosorted out by the sorter 22 and sent to the unnecessary mattercollecting portion 28. The wastes suitable for auxiliary fuel are allgeneral wastes excluding industrial wastes represented by wasteplastics, wastepaper, and wood wastes and household wastes. Syntheticrubber can be also recycled as auxiliary fuel.

The treated wastes suitable for the auxiliary fuel are further sifted bya regulator 29 according to their size. While powder is stored in apowder storage portion 30 as powder auxiliary fuel, wastes of certainsize are sent by a conveyer 31 to a granulating device 32 and formedinto pellet size while they are circulated between the granulatingdevice 32 and the next sieve 33 and are stored in a pellet storageportion 34.

The powder fuel and pellet products used 35 as the auxiliary fuel arecollected as incineration ash 36. The incineration ash 36 can be chargedinto a molding device 37 as it is or after it is kneaded with propersolidifying material, organic binder, or the like to be formed intodesired structural materials. As the structural materials, there are asystem house 38 for which the molded materials are used, alternativeconstruction materials 39, exothermic boards 40, for example. The powderfuel can be used in various forms. For example, the powder fuel can beused for a stove when it is let fall from an upper portion of a boilerstove against air blowing up like a tornado from a bottom portion andcompletely burned in the stove. Moreover, heat due to secondarycombustion of exhausted exhaust gas is exchanged with water to supplyhot water as a hot-water boiler. Moreover, it is possible to utilize thehot water for floor heating and road heating.

A reference numeral 41 designates a collecting portion of residuesregarded as unsuitable for fertilizer, feed, or auxiliary fuel thesorter 22. The collected residues are finally disposed of as treatedindustrial wastes 42.

POSSIBILITIES OF INDUSTRIAL APPLICATION

According to the organic waste treatment system of the invention, it isunnecessary to provide treatment apparatuses for respective types ofwaste as in a prior-art treatment system and it is possible to subjectgeneral wastes from home, ordinary offices, and the like as well asindustrial wastes including sludge, waste plastics, and the like totreatment such as decomposition by a hydrothermal reaction under asubcritical water condition. Therefore, it is possible to reduce costsof waste treatment. Moreover, the treated wastes can be taken out in thedried state and therefore can be sorted as they are and recycled asfertilizer, feed, and auxiliary fuel, which is extremely economical.

Furthermore, the treatment system of the invention can decompose anddispose of the waste plastics and waste rubber without burning them andtherefore does not generate harmful substances such as dioxin and can besaid to be a safe system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

A sectional view of an example of an organic waste treatment apparatus Ain a waste treatment system of the present invention.

FIG. 2

A block diagram of an example of the waste treatment system of theinvention into which the treatment apparatus A of FIG. 1 isincorporated.

EXPLANATION OF REFERENCE NUMERALS

-   -   1 Heat-resistant and pressure-resistant container    -   2 Waste charge port    -   3 Waste charging device    -   4 Discharge port    -   5 Discharge pipe    -   6 Screw blade    -   7 Shaft    -   8 Motor    -   9 Vapor generating device    -   9 a Intra-container vapor supply device    -   9 b Intra-wall vapor supply device    -   10 Pressure regulating device    -   11 a Intra-container pressure sensor    -   11 b Intra-double-wall pressure sensor    -   12 a Intra-container temperature sensor    -   12 b Intra-double-wall temperature sensor    -   13 Cyclone    -   14 Capacitor    -   15 Wastewater treatment setup    -   16 Vacuum pump    -   19 Central control unit    -   20 Discharge conveyer    -   21 Hopper    -   22 Sorter    -   26 Steam dryer    -   27 Sieve    -   28 Unnecessary matter collecting portion    -   29 Regulator    -   30 Powder fuel storage portion    -   31 Conveyer    -   32 Granulating device    -   33 Sieve    -   34 Pellet storage portion    -   35 Use of auxiliary fuel    -   36 Incineration ash    -   37 Molding device    -   38 System house    -   39 Alternative construction materials    -   40 Exothermic boards    -   41 Residue collecting portion    -   42 Treated industrial waste    -   k Clearance    -   GT Gas turbine    -   GE Generator

1. An organic waste treatment system for hydrolyzing organic wastes while stirring the wastes under a high-temperature and high-pressure environment and thermally decomposing or carbonizing the wastes in a double-walled pressure-resistant container, wherein the system comprises at least: water vapor supply means for supplying high-heat saturated water vapor into the container; pressure regulating means for regulating pressure in the container by using an on-off valve; and stirring means having a shaft for stirring the charged wastes in the container and provided to penetrate the container and the system includes the steps of: hydrolyzing the wastes while adjusting temperature to 230° C. or higher and pressure to 3 MPa in the container and stirring the wastes and thermally decomposing or carbonizing the wastes; adjusting the pressure in the container to atmospheric pressure or lower and discharging the treated wastes out of the container while maintaining a dried state of the wastes, and; sorting the discharged treated wastes and forming at least one of fertilizer, feed, and auxiliary fuel depending on types of the wastes.
 2. The organic waste treatment system according to claim 1 further comprising forcibly discharging means for forcibly discharging water vapor to discharge the water vapor generated in drying to an outside of the pressure-resistant container.
 3. The organic waste treatment system according to claim 2, wherein the discharged water vapor is used to operate a gas turbine to generate electricity by using the power.
 4. The organic waste treatment system of claim 1, wherein the dried state of the treated wastes is maintained by supplying high-heat water vapor into a clearance between an outer wall and an inner wall of the double wall of the pressure-resistant container and maintaining temperature at 160 to 180° C. and pressure at 1 MPa in the clearance.
 5. The organic waste treatment system of claim 1, wherein the organic wastes are at least one type of industrial wastes of sludge, waste plastics, wastepaper, wood waste, animal solid wastes, plant and animal residue, animal feces and urine, animal carcasses, and infectious specially-controlled industrial wastes.
 6. The organic waste treatment system of claim 1, wherein the organic wastes are at least one type of general wastes of general wastes from business activities, household wastes, infectious specially-controlled general wastes, separated garbage, and food residue.
 7. The organic waste treatment system of claim 1, wherein auxiliary fuel is formed as powder or pellets.
 8. The organic waste treatment system of claim 1, wherein incineration ash after use of the auxiliary fuel is molded by a molding device and used as structural materials. 